Relativity Explained: Time Dilation, Length Contraction and E=mc²
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- Опубликовано: 9 июн 2024
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Part 2:
• The Twin Paradox: Visu...
Really good explanation! I've been interested in this topic for a while and honestly your explanation of time dilation early in the video really made it click for me. Keep making videos- you've got a real talent!
I scrolled down to make this exact comment.
To everyone: The explanation given here is highly simplified, and the actual proofs involve highly complex mathematics (immensely complex ,but intuitive). However this is good enough for most people.
nirbhay thacker It still doesn't make sense
This makes total sense, try rewatching it, also i am an engineering student, so in physics we have the derivation for such things ( but not this equation) they involve very difficult physics and math, but it feels like life just went from 3D to 4D, it's very interesting. Once you understand it, it gets you hooked.
It's kinda staggering how much of a badass Einstein was. I hope one day I'll be smart enough to actually understand the progression of his formulations and understand the true beauty of his work.
The Rest Of Us, you make great educational videos that are very accessible. I think this is the simplest and the most informative explanation of the relativity theory I have come across (I don't have any physics background). Keep up the good work!
This is probably the best quick explanation I've seen to explain relativity. Good job, I'm hoping to see many more videos from you!
This is easily the best relativity explanation out there. Thank you for this
Hey, the rest of us!
I just found your channel a few hours ago and have been binge watching, basically...
Anyways, you just managed to explain special relativity and the speed of light better than anyone else has! I finally have understood the concept...
You're a great RUclipsr and deserve your presence on RUclips ;)
Don't forget that a lot of work on relativity was already done by Lorentz. The difference was that Lorentz did not believe it was actually happening, but considered it a mathematical trick.
ok now my respect for albert Einstein has increased 10 folds. :)
people still use the word "folds"??
Long live Palestine, Long live Gaza well no because it's "fold" in this context and it deals with orders of magnitude so yes if you want to express that then you use fold
@@WymanandBrad Long live the Zimbabwe space agency
Incredibly straight forward explanation using easy to understand references. Finally, after all these years of simply plugging in E=mc^2 to solve questions, I understand what special relativity is getting at...thank you!
I like how the cars at the end are moving at 1 billion km/h, more than 3x the speed of light.
so, he was more of a philosopher than a scientist at the beginning of his career.
This video had me understanding E=mc^2 better than 10 hours worth of researching. Great Video!
Excellent video!
Holy Heck what a great video! Keep on being awesome dude :)
Woah! Those trucks are moving at more than 3 times the speed of light!
+Joseph Hart Haha, ok - you made me curious: please walk me through the math you did :)
Well actually now that I've rechecked the numbers those trucks are actually moving just under the speed of light. I accidently divided 10^9 km/hr by 299 792 km/s without checking the units which is why I got a little more than 3. Sorry!
No Joseph you were correct. Using the silicon hyposphere equations it is trivially simple. The math checks out. This RUclipsr is clearly not on the same page as the majority of the scientific community. Next he'll try to tell you the earth isn't hollow! Don't believe the hype Joseph, the search for the truth will always win out!!!
this is the worst bait ever
Now I can truly appreciate how smart Einstein is. I will never be able to conjure this shit up in my brain
This is the best explanation of the theory of relativity I've ever come across - now it all makes sense! :D
this is the clearest explanation I've found. thank you!!
just loved this video... very easy to understand for a beginner.
Very good explanation! Thank you so much.
Simple and to the point! Looking forward to the one about general relativity!
Nice quick explanation of special relativity!
I saw the whole playlist! nicely funny and at good flow. Work on channel man. Even for fun.
I learned so much from this video. Thank you! :D
Could you make a video on general relativity? You're a great explainer
Nice video, I like to watch your videos :) and great informations ! helps me a lot to understand things c:
thanks for explaning so good to understand and giving us to think! Und du hast so einen super klasischen deutschen akzent im englischen obwohl du es perfect sprichst!
James Clerk Maxwell was a proponent of aether theory of electrodynamics, which is why he developed both an aether version and a field version of his equations.
you have produced this video pretty good, you should make more
You have a typo around 6:45. The relative speed that each truck observes in the other truck will be a bit bigger than 1 billion km/h (around 1.076 km/h) because of the uneven relativistic change in the observed time and length. Not two billion as Newton would have expected but more than one billion as the video shows. I'm wondering if 1 million km/h would be better since the relativistic relative speed is just slightly less than 2 million km/h. I don't know man, but despite the prattling, I do enjoy the video very much. Thank you The Rest Of Us!
this is a great channel
i have read special relativity but man your video is awesome keep making more like these....
Great work to the rest of us for making this complex idea so easy to understand!
“Genius is making complex ideas simple, not making simple ideas complex.” - Albert Einstein
That particle accelerator is pretty kickass.
Hey, amazing video. Can you please work on the general relativity one next! I wish this came out two weeks ago... I would have aced my midterm. The final is all on general relativity, so hoping it comes out soon!!
Wow this was so simple thank u so much!
The greatest video I have ever watched...!
love this video
This is awesome!
this just blew the crap out of my mind
You understand special relativity well. Because you were able to understand it simply.
Great work. (y)
i don't know what's more confusing, this video, or the fact that i understand it
great video!
00:00 "All quotes on the internet are true and told by me indeed" - Albert Einstein 2016, NY.
The quote at the beginning is a paraphrase of Richard Feynman's words which are in his biography and lectures. There are no valid sources stating Einstein said that.
Thank you!
You're a Genius
very nice!
That was really interesting
nice explanation
good channel
As a minor caveat to the comment on 'seeing' each other moving in slow motion, it's worth noting that relativistic Doppler shift is by far the dominant visual factor. Therefore, if observers are moving towards each other, they will actually see each other in fast motion...
the full equation is E^2 = (mc^2)^2 + (pc)^2 with p = velocity, think of the equation as a right triangle and E is the hypotenuse, and mc^2 and pc as the bases. it just bugs me when people omit the other bit of the equation and just give the part where p = 0
+Zachary Keller Why would that bug you? Because you saw a Minute Physics video about the expanded equation and now you think the p=0 version of it (which Einstein discovered first and is thus part of special relativity) is useless? Actually, the short form E=mc2 is the version most often used by physicist in daily life for practical purposes such as nuclear fission. So what exactly bugs you about it?
Mostly bugs me because I don't like it when people don't give the full equation for something and give the short hand, I've had a teacher who used to do this a lot and many of us would fail tests because the teacher’s short hand equation wouldn't work all the time. Also I knew about the full equation long before that minute physics video, although I did use its way of explaining it with the triangle.
Just want to point out, p isn't velocity. p is momentum. p = m * v
You did mention the equation right after an example with a rocket that was gaining momentum. I think it would have been better/less confusing to mention the momentum bit.
I've always thought that time dilation is PERCEIVEABLE time, as in someone in a spaceship sees stuff happening on earth with some delay, or some "slow motion". Not that the time is not constant/always there/always the same.
So the takeaway from this is that us literally just looking at something while going faster can change the length and mass of it.
Surely the trucks would change mass, and would have clocks that run slower etc, but just on a minute, even atomic scale?
Hi, I absolutely love your videos! So succinct and clear... I would love to see a video that explains why the speed of light is the limit (if that is answerable)... Einstein's special relativity is based on that postulate so I get stuck there without understanding why that's a thing. Oh and with that, why does light have to go at the same velocity in all reference frames? I think I'm missing something fundamental here...
What you ask is a very interesting question. The answer is: no one in the entire world knows why the speed of light is the maximum speed (or why it is what it is). We have simply observed, that there seems to be a maximum speed in the universe, which nothing can surpass. Gravity or magnetism, for example, also travel at this maximum speed. And since it is the maximum speed, it can't change for different reference frames.
If moving bodies shrink and gain more mass, would it mean that if you move a body fast enough, it'll become a black hole?
Special relativity could lead you to think that. Nevertheless, as Einstein later showed with his general relativity, "relative mass gain" is more tricky than he originally thought. So the short answer is no, fast moving bodies do not become black holes.
yeah i think thats what the idea of a black hole comes from - look up some documentaries, im sure you're on the right path
I guess I'll have to look into it
That is what I originally what I thought. If an object got into the realms of ~1 tredecillion km/h, I think that it'd probably get to a point, where it'd become a black hole.
yeah like charges being sent between atomic particles go at the speed of light and going past that does some weird stuff apparently
This clearly leads me to believe that Albert Einstein was a GENIUS.
Really, it is extremely hard for me to believe, let alone comprehend these things even though scientists have proven them. For someone to construct these explanations with such Beauty and Simplicity is nothing less than a miracle for me!
He was a lot more than a genius. His IQ was probably within the realms of 180-195. Genius status is at 140+ IQ. Then again, IQ isn't a very accurate measurement, and it really isn't very useful.
His IQ is probably equal to to the speed of light in km/h
Grapen Grollen lol
Around 1890 length contraction was already theorized.
Here is a problem with this scenario. I am firing a smooth ball at a wall with a 'set-force' spring mechanism so any fired ball has the same speed, (in order to parody that we cannot see a burst of light, only detect it's arrival, I don't need to watch the ball), and timing it's journey.
As it happens, a helicopter, aeroplane, micro-plane or some other flying device flies past and Albert, the pilot, looks down and times the ball through it's journey.
From his perspective, the ball travels along a triangle, just as in this scenario with light.
Is the pilot to believe that all balls always travel at the same speed, no matter what the speed of the source relative to the receiver?
Excellent video.
Would like to point out that, at the end, the two vehicles each moving 1bn km/h in opposite directions should have a relative speed of 2bn km/h, not 1bn km/h.
Edwin Chan No, 1b km/h is a relativistic speed. So from their perspective, they won’t have a relative speed of 2b km/h, which is the whole point.
I can follow your pace to understand what your saying
ay hol up *smacks lips*
if an alien in a ship going really fast just happens to observe me jumping into a swimming pool, i'll be falling in slow motion and be way heavier?
I can't even really understand this I can't imagine how someone thought it up in the first place.
I have a question: At 6:03... when it says "the missing mass is transformed into energy"... if we couldn't weight it... how do we know where it went?
what's he talking about......it seems to be mind-boggling......
hey, this may be a dumb question but I was confused so Ill ask anyways. in the example you have for time dilation, the light particle travels at the same speed for the astronaut but to him the distance seems longer, and as speed of light is constant, time has to be longer as well.
But even if the astronaut thinks he is a resting body, in reality isn't the spaceship the moving body while the earth and moon are resting? I understand what you said in theory, but when I think of it practically using that example it's gets confusing, as I keep thinking that even if relative to the astronaut time seems longer, time still isn't actually longer is it?
+Shahnila Nahid Time is actually longer. It gets stretched. The whole point of relativity is that these are all REAL effects. If it were just an 'illusion', scientists wouldn't care about relativity. They do care, because they need to consider the laws of relativity everyday in their labs. What Einstein told us, is that time is a relative thing, which ticks at different speeds in different places. Fascinating, isn't it? It's not intuitive to us, because our brains didn't evolve to understand relativity. But it's nonetheless true and was tested endless times by now.
For "Length Contraction" at 3:11 and the "Light Clock" example, if the light clock emitted a signal that implied "yes, both photos met at the center at the same time" ... then where is the relativity? No matter how many spaceships "observe" the photons or not, or how fast those spaceships are moving (or not), the light clock (w.r.t. its own reference) will keep emitting the signal.
So how does it matter how it looks to anyone else "outside" of that reference? The event (meeting of photons at the same time) happened, continues to happen and nothing can change it.
So ... ?
He explained this in the video, for the ships the photons would be moving at different times unless there was light contraction. Which he also explained.
Ummm... in the ship example: The moon isn't moving past earth, it's orbiting it, meaning that the diagonal thing doesn't really work.
My head is going to explode
At 3:08 - wow, your german is great :)
the full equation of E=mc^2 is a much better version E^2=(mc^2)^2+(pc)^2 as it is Pythagorean and it shows light has energy because light has momentum but no mass
Maybe on the wrong path here but isn't one of the rules of thermodynamics that energy can be turned to mass and mass to energy but nothing is ever created or destroyed? So in the case of a moving object gaining mass is that really an actual thing? Does it actually gain mass or is that just a way of catering for the difference in instrumental measurements that occurs when measuring something travelling at high speeds?For example if a meteor flew past earth at very high speed and our measurements determined it was 1 million tons in mass and a certain size in diameter if we somehow managed to slow the meteor without destroying it and brought it to earth and then measured it again would it be both much lighter and much larger than the initial measurements suggested?I'm lost
What if you were to get a rope long enough to go to mars from earth without any slacks and pull it. Would the pull come immediatly faster than the speed of light or take nine minutes to get there?
Einstein wasn't so smart. He thought that speed starts with a c
Actually his original papers had "V", but Maxwell (I think) suggested changing that to avoid confusion with other velocities.
Speed of causality bro
"C" stands for "constant", because the speed of light is a constant
Also, "c" stands for "constant"... because the speed of light is a constant
Also, "c" stands for "constant"... because the speed of light is a constant.
What is that wonderful old photo in color at the end of the video?
en.wikipedia.org/wiki/Solvay_Conference
wasn't that the conference that pretty much said that newton was sorta wrong when it came to really small fast objects, butright when it came to large slow ones
This video has as it's coefficient of variation of light speed entirely dependent and relevant to time. Light is light and time is time. If you had a very precise watch and you were watching the sunrise, at the equator, you would be racing 1000 mph towards light. Yet your watch remains constant.
+Chad Hurley You sir, don't make any sense. Please rephrase.
Also, if that makes any difference to you, the effects of 1000mph on time has been experimentally observed using airplanes and atomic clocks.
OK THEN. Just tell me why I take longer to pee when I drink more beer. I GOT YOU THERE !
+Chad Hurley Your question is beyond the scope of special relativity.
If time ticks "normally" on earth and on the ship its slower why does the person on the ship sees the time on earth ticking slower?Isn't he supposed to see it ticking faster?!! please reply
Can someone point me to the background soundtrack used for this video ?
I came up with that same failled experiment.
Albert was a fucking genius , I can understand the concept, but for him to come up with this theory by himself is MINDBLOWING
Theoretically speaking, don't the objects become weight(mass)less aproaching the light speed, I mean turn (their mass) into energy? Because objects with mass cannot achieve light speed for what I know. Only bodies that can do that are photons, right? (because they don't have any mass)
Shouldn't the trucks' relative speed be 2 billion km/h given that their individual speed (relative to observer) is 1 billion km/h?
No you have to use Lorentz transformations to account for separate reference frames. You're applying Galilean transformations which do not consider relativity.
Holo I'm excited to say that I don't understand what that means at all - which means I have a lot of new stuff to learn.
So is the relative speed to the earth really the same as the relative speed to the other truck moving toward the reference frame? Or is it just different from 2 billion km/h?
WHEN WILL THE GENERAL RELATIVITY VIDEO COME OUT
This all made way too much sense.
What's the music in this video throughout the first minute or two?
I feel as if your representation of time dilation is actually and illusion. the vertical movement does take the same time but the extra length is added is an effect of the astronaut moving. I'm confusing myself a bit so I would really appreciate a further explanation of why this is not an illusion.
That's the weird bit about SR, it's counter intuitive in that regard.
Wow wow wow!
Einstein is a time traveller and just recited his high school textbooks
He or someone else would have had to come up with it first before he could recite it. Because someone had to put it in the books didn't they?
Song? I've heard it so much but dont know the name.
High speed.
Can someone well versed in mass-energy equivalence tell me if mass is just the amt of energy a system has. Instead them being interchangeable, mass is simply a property of energy.
*Instead of
does that mean we could theoretically make atoms / turn atoms into energy?
Nuclear fission?
This all works out in relativity to time itself, but let's say that the twins were to be born and die at the same exact time. Both twins would die at the same time, although one would be travelling a light speed while the other on is one earth, right?
If you constrict the paradox to an inseparable event then yes, just like the light clock relativity cannot separate the photons hitting at the same time. Constricting the paradox in such a way stops it from being useful though.
I just wanted to make sure that flying through space for a long time isn't any better than staying on earth as far as aging goes.
Thanks.
If you could go near the speed of light, even .3-.4 c and at some point you return to Earth (acceleration -> change of inertial frame) then you will be younger than a version of you that stayed on earth.
The paradox is that each twin sees the others clocks move slower so they should both be younger
and it takes 1.8 sec to reach the moon and back
Round-trip travel time ranges from 2.33 to 2.71 seconds.
Source: Lunar laser ranging: the millimeter challenge
Dosen't speed of light changes with change in medium?
+sudaksh mishra You're right, it does. What I am referring to is (of course) the speed of light in a vacuum, which is - as far as we know - the maximum relative speed that can be achieved in our universe. Personally, I usually prefer to say "speed of gravity", since it's the same as c and medium independent.
The Rest Of Us Got it, but can we also say that taking the speed of light as constant in a given medium(i.e. there is no density change), for observers inside that medium, will time dilation be achieved faster for a fast moving particle than to a case where the whole setup is in vaccum? Or does this mean light particle in a medium would see it's time move faster than a light particle in vaccum?
There's nothing magical about "the speed of light" in a literal sense. Rather think about it as the maximum speed of the universe. In a vacuum, light happens to reach the maximum speed of the universe. In water, for example, light is much slower than the maximum speed of the universe, but gravity still travels at the maximum speed.
So to answer your question: Relativistic effects occur, when you get closer to the maximum speed of the universe.
Why whould both see each other in slow motion?
Only the earth would see the ship in slow motion. The ship sees the earth in time laps. Every Second on the ship is >1s on earth. So an earth everything is faster.
6:47
Nope, that's ftl
wait wait wait wait. i thought that particle accelerators could only speed up particles to 50% the speed of light or am i wrong?
nah , usually more than 90%
Damn, that's amazing!
+Why is it that I can write so much for my username it makes no sense Because the nature of most expt. performed in particle physics are colliding particles in v. high speed. From the mass gain we can "create" more particle than we initially have.So we can discover new ones from known ones. :-D but it requires a lot of energy to accelerate and equipment must be stable and precise.
So where's the line of speed between not gaining mass and gaining mass?
He explained it slightly wrong, there is no "line" where this things start to happen. Even if you walk you will get heavier, thinner and your clock slows down, but those effects are so small that they are almost not there.
The relative speed of the trucks would be 199.9999999999991km/h if I calculated it correctly
there is something I still don't quite understand, why observer in Earth would see the clock in the spaceship slower, Shouldn't be faster???
+Francisco Javier Delgadillo Casas This is very difficult to understand, because it is not intuitive.
Maybe referring to the second thought experiment helps: Imagine there is a light clock on the spaceship. If somebody from earth observes the ship flying by with high speed, he will see the photon of the light clock inside the ship move along a zick-zack path. This generates the same conclusion, as when the astronaut sees the photon between earth and moon moving in a zick-zack path. The photon always takes longer along a zick-zack. Both see each other's clocks running slowly. The effect is symmetrical.
Now, once they reunite on earth, the time that has passed for both of them will be different. (To understand this better, it requires another thought experiment, which I am currently working on - but don't wait for it. Might take a while until the video comes out.)
+The Rest Of Us and I though I ve undestood this theory, but when you can explain it simply you already undestand :P I would had imagined the spaceship clock from Earth perspective runs faster
+Francisco Javier Delgadillo Casas No, because when things move faster time effects them slower. Like when you move extremely fast and things around you seem to slow down, this is not just by comparison. Take Sonic for example, when he moves faster, everything around him moves slower. This is not only by comparison and not only because he is able to think fast as well and react faster, everything that isn't moving at the same speed as him slows down (to him) because he is moving so fast that everything else becomes slow-mo.
+The Rest Of Us I'd love another video about this! Please try to make it as soon as possible and as looong and informative as you can!
That would require general relativity, because special relativity requires that the observers never accelerate; therefore, the twins would never see each other again, and would never settle the question of whose clock ran faster and who is older. However, if the twin on the spaceship returns home, the spaceship must have changed direction at some point in the journey. Since the spaceship is accelerating relative to the overwhelmingly larger mass of the universe, while the twin on earth is not except for earth's movement around the sun, etc. Since the situation is asymmetrical because of the acceleration, the spaceship twin is younger upon arriving home than the earth twin. If the trip is fast enough and long enough, many centuries may have passed on earth, and the spaceship twin would be, in effect, a one way time traveler.
Since arriving home, astronaut Scott Kelly, who spent almost a year on the ISS, is a few nanoseconds younger than his twin brother Mark, who stayed on earth as part of a science experiments (both were astronauts, but Mark has retired from active flight).